1. Field of the Invention
This invention relates to a limit mechanism, more particularly to a limit mechanism for a manually operated door machine, which is utilized to control a door curtain in such a manner that the door curtain stops accurately at an upper stop level or a lower stop level.
2. Brief Description of Prior Art
In a conventional manually operated rolling door machine, there are a pair of L-shaped blocking plates arranged back to back attached to the end portion of the door curtain wound by the reel, which is utilized to block the door curtain from exceeding the upper stop level in the ascending stroke and the lower stop level in the descending stroke. In the operation of the conventional manually operated rolling door machine, a user generally will stop exerting force by visual estimation as soon as the door curtain arrive near the upper stop level or the lower stop level with the result that this operation is not reliable. Incautiously, the user will make a lot of noise in operating the door curtain due to impact as the blocking plates collide with a stop means at the upper stop level or the lower stop level, even subjecting the door curtain to an impact and causing the squeezing deformation of the door curtain. Hence, there is still room for further improvement in implementation as well as in structure of the door machine.